The present disclosure relates generally to computers, and more particularly, to a method and apparatus for the identification of liquid crystal display panels for notebook computers.
Notebook computer manufacturers use a variety of LCD panel types and vendors in the manufacture of notebook computers to reduce cost and to increase production levels. In addition, each type of LCD panel typically have unique operational timing and include other operational considerations as well. This requires that each LCD panel model have a unique Panel ID (i.e., panel identification), wherein the panel identification provides an indication of the LCD panel resolution and type. Still further, for a given single notebook computer model, the computer model may have a large number (e.g. as many as twenty four (24) or more) unique Panel IDs for the LCD panels which are used with that particular computer model. In addition to identifying panel type and resolution, it would also be desirable to identify the vendor associated with a given LCD panel display from the Panel ID.
Currently, there are two basic methods in common use to obtain the Panel ID, including dedicated Panel ID lines and multiplexed Panel ID lines. With the use of dedicated Panel ID lines, the number of connections between the LCD panel and the computer increases. With respect to the multiplexed lines, the multiplexed Panel ID lines work as dedicated lines at certain times. To establish 24 Panel IDs would require at least five (5) dedicated lines and input/output (I/O) pins encoded with respective identification values. The later presents additional cable design challenges.
In prior systems, an LCD panel type has been indicated by providing a number of additional pins from the LCD panel to the base unit of the notebook computer system. Thus, by encoding the additional pins with certain values, the computer is able to determine the type of LCD panel being used. A disadvantage of this method, however, is that a number of extra wires are required to be routed from the LCD panel to the base unit of the notebook computer system. Further, as the number of panels that can be used with a given notebook computer system changes, so must the number of pins. Thus pin and wiring limitation problems and increased costs are quickly reached. Logistical and standardization problems with LCD panel vendors also occur.
In a prior system, four (4) dedicated panel ID lines were used to identify up to 16 different LCD panels. If additional LCD panel manufacturers beyond sixteen were to be enlisted for supplying panels for the given model of notebook computer, then the number of available unique LCD panel identifications is quickly used up.
To further illustrate the problem in the art, currently, dedicated lines are used which extend from a video controller, located in the base unit of the notebook computer, to a flex cable or ribbon cable which connects to the LCD panel. In other words, the flex cable extends from the LCD panel to the video controller on the system board or motherboard of the base unit. The dedicated lines are either pulled high (+Vcc) or low (GND) to indicate a logical one "1" or a logical zero "0", respectively. With four dedicated lines, then a limit of sixteen (16) different LCD panel IDs are possible. The four dedicated lines take up space on the flex cable. In addition, the extra dedicated lines present a mechanical space problem, since it would be most desired to keep the flex cable as small and narrow as possible for assistance with a mechanical design of the hinges used for attaching the LCD panel to the base unit of the notebook computer. Thus, mechanical space limitations are a concern. Still further, with the nature of some signals in the flex cable which pass by the static lines (i.e., static lines including the dedicated panel ID lines), there might be electromagnetic interference (EMI) undesirably transferred onto the static lines. It is thus desired to reduce the pin count required for establishing necessary connections between the LCD panel and the base unit of the notebook computer, however, while at the same time increase the number of panels to be supported. For example, to support 32 panels, additional lines would be needed using the prior known identification methods. With the prior methods and apparatus, computer board space and cable space are undesirably taken up.
In U.S. Pat. No. 5,495,263, issued Feb. 27, 1996 and entitled "Identification of Liquid Crystal Display Panels", a method is disclosed for identifying the type of LCD panel used in a portable computer system based on the frequency of an oscillator signal of a DC-to-AC inverter located in the LCD panel. The '263 method relies upon the oscillator signal frequency to drive a system counter located in the base unit of the computer. However, the '263 method is subject to imperfections and variations. For example, components tend to drift over time and with varying temperatures. As a result, the oscillator signal of the LCD panel is subject to variation. In addition, the '263 method relies upon the use of a non-deterministic frequency. That is, the frequency is not an absolute and is subject to fluctuation. Errors can thus occur in panel identification as a result of quite a bit of variation in measured frequency. In addition, the '263 method uses an ASIC (application specific integrated circuit) for the video controller for panel identification purposes, however the use of an ASIC is not conducive or readily alterable as a standard solution. Furthermore, the '263 method relies upon one way oscillator signal transmission from the LCD panel to the base unit and does not utilize any feedback during a panel identification.
A method and apparatus of identifying the LCD panel resolution, type and a respective vendor is thus desired which does not require unnecessary additional pins or components. It is further desired that panel type and respective vendor be accurately determinable.